1. Field of the Disclosure
The present disclosure relates to a perpendicular magnetic recording head that records information by applying a perpendicular magnetic field to a recording medium, and to a manufacturing method thereof.
2. Description of the Related Art
As is widely known, a perpendicular magnetic recording head has a main magnetic pole layer, a return path layer, a nonmagnetic insulating layer that is disposed between the main magnetic pole layer and the return yoke layer, and a recording coil layer that is disposed in the nonmagnetic insulating layer and that provides a recording magnetic field to the main magnetic pole layer and the return yoke layer. The main magnetic pole layer and the return yoke layer are disposed in a recording medium with a predetermined spacing defined therebetween. The main magnetic pole layer is magnetically coupled to the return yoke layer at the side remote from an opposing surface opposite the recording medium in the height direction. Once electricity is supplied to the recording coil layer, a recording magnetic field is induced between the main magnetic pole layer and the return yoke layer and flows in the recording medium-opposing surface between the main magnetic pole layer and the return yoke layer, thereby generating a recording magnetic field. The recording magnetic field enters a hard film of the recording medium in a perpendicular fashion from a front end surface of the main magnetic pole layer exposed to the recording medium-opposing surface. The recording magnetic field passes through a soft film of the recording medium and returns to the return yoke layer to thereby complete magnetic recording on the recording medium in the portion that opposes the main magnetic pole layer. In the vicinity of the return yoke layer, in order to secure a patterning precision of layers to be laminated above the return yoke layer, a planarized nonmagnetic layer composed of a nonmagnetic material such as Al2O3 or SiO2 is formed. A planarizing process is performed so that the upper surface of the planarized nonmagnetic layer and the upper surface of the return yoke layer are disposed on the same surface.
In such a perpendicular magnetic recording head, the return yoke layer is generally formed in a rectangular shape in top view. However, when the return yoke layer is formed in the rectangular top shape, an external magnetic field or the recording magnetic field returning from the recording medium is likely to concentrate on angular parts of the return yoke layer including the front end surface thereof exposed to the recording medium-opposing surface and both end surfaces thereof in the track width direction. In such angular parts of the return yoke layer, information is unintentionally written to or erased from the recording medium. According to a proposal regarding prevention of the undesired writing or erasure by the return yoke layer, inclined or curved surfaces are formed at both sides of a return yoke layer (or an auxiliary magnetic pole layer) in the track width direction. The inclined or curved surfaces gradually broaden the dimension of the return yoke layer in the track width direction as the inclined or curved surfaces extend from a front end surface of the return yoke layer exposed to the recording medium-opposing surface in the height direction. A perpendicular magnetic recording head having such inclined or curved surfaces is disclosed in Japanese Unexamined Patent Application Publication Nos. 2004-039148 and 2004-280921. According to the perpendicular magnetic recording head, an external magnetic field or the recording magnetic field returning from the recording medium is absorbed by a wide range of areas of the inclined or curved surfaces, thereby suppressing the recording magnetic field concentration. Therefore, it is possible to prevent the undesired writing or erasure by the return yoke layer, thereby improving resistance to an external magnetic field and reliability.
However, when the inclined or curved surfaces are formed at both side of the return yoke layer in the track width direction, a planarized nonmagnetic layer that is exposed to the recording medium-opposing surface and that covers from the recording medium-opposing surface to the inclined or curved surfaces peels off or cracks during a polishing processing for forming the recording medium-opposing surface or during a post-process cleaning (ultrasonic cleaning). Although the resistance to the external magnetic field increases as the angle (an angle between the recording medium-opposing surface and the inclined or curved surfaces) of the inclined or curved surfaces at both sides of the return yoke layer in the track width direction decreases, the peeling or cracking of the planarized nonmagnetic layer becomes more prominent as the angle decreases.